Although the major environmental and personal risk factors for heat-related illness (HRI) are known and California regulations have been enacted to protect workers, deaths and significant numbers of HRI continue to occur, particularly in agriculture. There continue to be many uncertainties surrounding factors that place workers at risk for HRI and employers' ability to utilize risk reduction strategies for worker protection. Missing from occupational studies on factors contributing to HRI are considerations of the metabolic heat load from working in diverse agricultural environments, and the socio-cultural factors affecting the mostly immigrant workers' work practices/behaviors. Without thorough understanding of these aspects, effective strategies to reduce agricultural HRI are diminished. This multidisciplinary effort brings together investigators from medicine, epidemiology, public health, physiology, anthropology and community outreach/education who are uniquely positioned to address HRI in agricultural populations. Our goal is to obtain novel data on internal body temperature as it relates to crop type and geography, external heat and internal metabolic loading, including accounting for work type and personal factors. Our innovative approach will obtain critical information on knowledge, work practices and social-cultural issues that impact a worker's decisions with regard to HRI prevention. By combining these approaches, we aim to develop protective strategies to be translated and broadcast through outreach and education programs. The specific aims of this proposal are: (1) Increase understanding of the physiological responses to increased environmental heat and physical exertion among farmworkers through the analyses of personal characteristics, monitors and sensors, and use the protocols developed to generate and validate risk models. 2) Examine socio-cultural perspectives of HRI using focus groups and key interviews, and identify barriers to adoption of prevention strategies and potential solutions acceptable to all parties. (3) Assess normal practices of farmworkers that impact HRI risk using epidemiological techniques. (4) Increase awareness of HRI as a credible personal risk to farmworkers, and translate project findings into HRI prevention strategies.